Concept:Family relationship questions are solved by tracing each relation step by step.Explanation:Rohit is Dev's son.Poonam is Mehak's only sister.Dev is Mehak's brother-in-law.Since Poonam is Mehak's sister, Dev must be Poonam's husband.So Rohit is the son of Poonam and Dev.Therefore, Rohit is Mehak's nephew.